The biggest problem is that you want to make sure that the software installed on your system will be compatible with software installed by Debian. Generally, Debian Stable is your best bet, but software versions are generally quite outdated by the time they make a release.

Is there a tutorial for GNUstep users?

I can't remember who it is here that makes the Debian packages, but you might want to check with that person and see what he does.

Are thereany GUI-based applications that help with the build process?

I doubt it, but you can check if there's anything being mentioned on the tutorial.